The invention relates to a disk brake, preferably a compressed air (pneumatic) operated disk brake, comprising a caliper which encompasses the brake disk, and an actuating device which features a rotary lever supported on pivot bearings. The actuating device is arranged on one side of the brake disk. The rotary lever rests against an eccentric device featuring a pressure element and acts directly or indirectly upon a cross member, which can be displaced in relation to the brake disk.
In generic disk brakes, the transmission of forces occurs when the brake cylinder is operated through a rod, which acts upon the rotary lever. The rotary lever is supported in the caliper housing by means of a pivot bearing. A cylindrical pivot-bearing shaft of an eccentric device is arranged in a recess in the rotary lever offset against the axis of rotation. Pivoting of the rotary lever causes a spring-loaded cross member to be displaced transversely relative to the surface of the brake disk. On the side facing away from the brake disk, this cross member engages at least one rotary spindle with a pressure plate, which presses against the brake shoe when the brake is operated, so that the brake lining contacts the brake disk. The generic disk brake can be executed as a single-spindle device or as a double-spindle device.
In known disk brakes, the moveable components, particularly the support of the eccentric device and the rotary lever against the housing, are to some extent executed as maintenance-free plain bearing half liners or as roller bearings. The rotary lever is supported in semi-cylindrical plain bearing half liners in the area of the housing facing away from the brake disk. The eccentric bearing is supported eccentrically to the bearing of the rotary lever in a semi-cylindrical recess in the rotary lever. A roller bearing in the form of a semi-cylindrical liner is inserted into this recess. Force is transmitted through the cylindrical shaft.
When the disk brake is operated, transverse forces develop due to the diagonal running of the bearings, which is caused by tolerances and by deformations linked to operating conditions, as well as by the vibration stress occurring during vehicle operation and the resulting forces of gravity. Consequently, corresponding locking elements for the rotary lever and for the cylindrical pressure elements arranged in the ball cups are needed to transmit the transverse forces. In addition, mechanically tooled guide surfaces are also necessary. The guide surfaces and locking elements not only increase production costs, but also increase the complexity of assembly of the disk brake. In addition, susceptibility to failure is increased.
Consequently, the underlying problem behind the invention is to design a compressed air operated disk brake using a simple design, so that the transverse forces occurring upon operation of the brake can be transmitted without locking elements and without guide surfaces. In addition, the disk brake should continue to exhibit high stability under load and should be designed in compact form.
This problem is solved by providing a disk brake wherein at least one pressure element of the eccentric device is designed to be essentially spherical or oval-, and/or barrel- or bale-shaped, thus comprising a spherical pressure element.
The transverse forces occurring during the braking process are now no longer removed by means of additional locking elements and the guide surfaces that are necessary as a result, but rather through the spherical pressure elements themselves. Consequently, the design can be manufactured in an especially cost-efficient manner, due to the reduction in the number of components, and, furthermore, is easily assembled. As the number of components is reduced in comparison to known designs, susceptibility to failure is reduced.
An especially advantageous embodiment of the invention is characterized by the fact that the spherical pressure elements are supported in essentially dome-shaped plain bearing half liners, which, in a structurally simple manner, interact with the spherical pressure elements to absorb the transverse forces that occur. The spherical pressure elements or their plain bearing half liners can be inserted into essentially dome-shaped recesses in the bridge or cross member and the rotary lever or in the caliper and the rotary lever.
Various embodiments of the invention can be formed. According to a first exemplary embodiment, the bridge acts upon a single rotary spindle with a pressure plate essentially centered in the bridge, wherein the cross member runs at an angle to the rotary spindle and is supported on the rotary lever by one of the spherical pressure elements on each side of the rotary spindle.
Alternatively, it is contemplated that the cross member acts upon a single rotary spindle essentially centered in the bridge, wherein the bridge runs on both sides of the pressure element and engages the rotary lever, which is supported by the spherical pressure elements on the caliper.
In addition to the single-spindle embodiments, corresponding double-spindle designs can also be used. Thus, for example, it is advantageous if the cross member acts upon two pressure plates and/or rotary spindles arranged in parallel to one another, wherein the cross member is supported by at least two of the spherical pressure elements on the rotary lever. Alternatively, the cross member acts upon two pressure plates and/or rotary spindles arranged in parallel to one another, wherein the cross member contacts the rotary lever through a pivot bearing, which is supported by at least one of the spherical pressure elements on the caliper.
The plain bearings are easily fixed in place by attaching or molding at least one peg or protrusion, to secure against torsion, to the sides of each of the dome-shaped plain bearing half liners facing the recesses, with the peg or protrusion engaging a correspondingly shaped pocket hole in the bridge/cross member or the part of the caliper or the rotary lever facing away from the brake disk.
The protrusion can also be designed to accept a lubricant, as either a hollow peg or hollow protrusion, which is open to the bearing surface of the ball cup.
As the number of components is reduced in comparison to known designs, the invention also reduces susceptibility to failure. Normally, it is not necessary to feature all plain bearing half liners as ball cups. Rather it is sufficient to feature at least one plain bearing half liner in this form. In another embodiment, it is provided that at least one of the spherical pressure elements is inserted with a positive fit into the corresponding ball cup, while the remaining roller bearings are moveably inserted into the dome-shaped plain bearing half liners. This guarantees axial locking. However, tolerances and deformations linked to operating conditions can be absorbed in the corresponding components, as there is a predetermined and limited mobility of the components inserted in the dome-shaped plain bearing half liner. The dome-shaped plain bearing half liners are advantageously oval-shaped for moveable acceptance of the eccentric device and/or the roller bearings. However, there is relatively little play.
The spherical pressure elements can be cost-efficiently designed as roller bearings, which are commercially available from relevant manufacturers. They generally provide extremely high surface quality, as the maximum peak-to-valley height is two one-thousandths of a millimeter (0.002 mm). The dome-shaped plain bearing half liners are preferably manufactured from a suitable, highly stress-resistant, plain bearing half liner material (e.g., a composite bearing with polymer sliding coating). Alternatively, the dome-shaped plain bearing half liner can also be made of graphite.
Alternatively, a suitable plain bearing material can be applied directly to the surface of the dome-shaped liner for acceptance of the ball, e.g., in the form of a sliding sheet.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.